"A nudibranch with hot pink and orange fluorescent donut rings, I'd like to see that! It's not every day that you come across one the rarest nudibranchs in the Pacific region"
The Donut Nembrotha (Nembrotha roseannulata) is a very unique nudibranch species that has only been recorded from a couple of locations in Australia. Even though it is large brightly coloured nudibranch species it is rarely seen by scuba divers.
There is one known location in the world where this species can be regularly encountered. The location is Cabbage Tree Island off Port Stephens in New South Wales - Australia where it is known to occur on the sheltered western side of the island in depths of 7 to 16 metres. On the western side of the island grows a purple ascidian (Sigillina cyanea) which is the only food source that the Donut Nembrotha is known to feed on. If divers closely examine the purple ascidians they may be fortunate enough to find a Donut Nembrotha feeding or laying its eggs. This species has also been seen with the tropical Imperial Shrimp (Periclimenes imperator) hitching a ride on its back.
Dr Richard Wilan, Curator of Molluscs at the Northern Territory Museum also has records of this species from the Great Barrier Reef and the Solitary Islands Marine Park in New South Wales.
The Donut Nembrotha can be recognised by it's green coloured mantle and the under body is purple in colour; a very similar colour to the ascidian that it feeds on. On the body there are large pink rings that look like donuts, hence it's common name. The rings in the larger adults are generally fluorescent bright pink whilst the donut rings on the juveniles tend to be bright orange in colour. The Donut Nembrotha (Nembrotha roseannulata) is known to grow to at least 12cm in length.
If you are interested in seeing or photographing this amazing nudibranch head to Port Stephens in New South Wales and talk to the local dive shop (Let's Go Adventures) about getting on the short boat ride out to Cabbage Tree Island. It is well worth it.
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